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4. Pediatrics MCQs

Practice Set 194 of 334

This practice set contains high-yield board review questions covering key concepts in 4. Pediatrics. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 3861

Topic: 4. Pediatrics
A 6-year-old child presents with severe bowing of the proximal tibia. Radiographs demonstrate depression of the medial tibial plateau with a physeal bar, consistent with Langenskiöld stage VI infantile Blount disease. What is the most appropriate surgical intervention?
. Observation and long-leg bracing
. Proximal lateral tibial epiphysiodesis alone
. Medial plateau elevation with interposition and metaphyseal corrective osteotomy
. Distal tibial dome osteotomy
. Contralateral proximal tibial epiphysiodesis

Correct Answer & Explanation

. Medial plateau elevation with interposition and metaphyseal corrective osteotomy

Explanation

In advanced Blount disease (Langenskiöld V-VI) with a physeal bar and significant medial plateau depression, bar resection and intra-articular elevation of the medial plateau combined with metaphyseal correction are required.

Question 3862

Topic: 4. Pediatrics

A 4-year-old girl has a congenital femoral deficiency with a current leg length discrepancy of 3 cm. Using the Paley multiplier method, what is the predicted discrepancy at skeletal maturity?

. 3 cm
. 4 cm
. 6 cm
. 9 cm
. 12 cm

Correct Answer & Explanation

. 6 cm

Explanation

The congenital multiplier for a girl at chronological age 4 is approximately 2.0. Therefore, multiplying the current discrepancy of 3 cm by 2 yields a predicted discrepancy of 6 cm at skeletal maturity.

Question 3863

Topic: 4. Pediatrics

An obese 3-year-old boy presents with progressive bilateral genu varum. Radiographs show a medial metaphyseal beak and a Drennan's angle (metaphyseal-diaphyseal angle) of 20 degrees. What is the primary biomechanical derangement leading to this condition?

. Excessive tensile forces on the lateral physis
. Premature closure of the entire proximal tibial physis
. Hueter-Volkmann principle acting on the medial proximal tibial physis
. Pathologic fracture of the medial metaphysis
. Overgrowth of the fibula relative to the tibia

Correct Answer & Explanation

. Hueter-Volkmann principle acting on the medial proximal tibial physis

Explanation

Infantile Blount disease is driven by the Hueter-Volkmann principle. Increased mechanical compressive forces on the posteromedial proximal tibial physis suppress its growth, leading to progressive varus and internal rotation.

Question 3864

Topic: 4. Pediatrics

A 7-year-old child undergoes lateral tension band plating (guided growth) of the distal femur for genu valgum. Three months post-operatively, radiographs show backing out of the diaphyseal screw. What is the most likely surgical cause?

. Placement of the screws too close to the physis
. Using fully threaded screws instead of partially threaded
. Unrecognized metabolic bone disease
. Insertion of the screws divergent rather than parallel
. Premature physeal closure

Correct Answer & Explanation

. Insertion of the screws divergent rather than parallel

Explanation

Tension band plates for guided growth require screws to be placed parallel or slightly convergent to allow the plate to act as a flexible hinge. Divergent screw placement prevents this toggling, drastically increasing stress and leading to screw back-out or breakage.

Question 3865

Topic: 4. Pediatrics

A 12-year-old boy is undergoing a 6 cm tibial lengthening over an Ilizarov frame. During the consolidation phase, he develops a fixed 20-degree equinus contracture. Which biomechanical factor primarily drives this complication?

. Overactivity of the tibialis anterior muscle
. Tension on the gastrocnemius-soleus complex stretching across the knee and ankle
. Direct injury to the common peroneal nerve
. Failure to include the midfoot in the external fixator
. Disuse atrophy of the deep posterior compartment

Correct Answer & Explanation

. Tension on the gastrocnemius-soleus complex stretching across the knee and ankle

Explanation

Tibial lengthening increases tension on the multi-articular gastrocnemius-soleus complex, which crosses both the knee and the ankle. This relative muscle shortening frequently results in a rigid equinus contracture if not aggressively stretched or braced.

Question 3866

Topic: Pediatric Upper Extremity & Spine

A 14-year-old male presents with a leg length discrepancy. A scanogram confirms the right femur is 3.5 cm shorter than the left. He is at Risser 4, and his bone age matches his chronologic age. Which of the following is the most appropriate management?

. Shoe lift only
. Contralateral distal femoral epiphysiodesis
. Right femoral lengthening via distraction osteogenesis
. Right femoral lengthening via an intramedullary lengthening nail
. Contralateral femoral shortening osteotomy

Correct Answer & Explanation

. Contralateral femoral shortening osteotomy

Explanation

Because the patient is near skeletal maturity (Risser 4), an epiphysiodesis will yield minimal correction. For a 3.5 cm discrepancy at maturity, a contralateral acute shortening osteotomy is reliable and avoids the higher complication rates associated with lengthening procedures.

Question 3867

Topic: Pediatric Lower Extremity

An infant with Proximal Focal Femoral Deficiency (PFFD) is evaluated. Radiographs show a severely dysplastic proximal femur with no radiographic evidence of a femoral head or acetabulum. According to the Aitken classification, what is the grade of this deformity?

. Class A
. Class B
. Class C
. Class D
. Class E

Correct Answer & Explanation

. Class D

Explanation

Aitken Class D PFFD is characterized by the complete absence of both the acetabulum and the femoral head. It is also associated with a severely shortened and dysplastic femoral shaft.

Question 3868

Topic: 4. Pediatrics
A 9-year-old obese male presents with progressive bowing of the left leg. Radiographs reveal a prominent step-off and depression of the medial tibial plateau with an osseous bridge, consistent with Langenskiöld stage VI late-onset Blount's disease. Which is the most appropriate definitive surgical intervention?
. Observation and bracing
. Proximal tibial valgus osteotomy alone
. Epiphyseal bar resection and interposition grafting with valgus osteotomy
. Distal femoral varus osteotomy
. Lateral hemi-epiphysiodesis of the proximal tibia

Correct Answer & Explanation

. Epiphyseal bar resection and interposition grafting with valgus osteotomy

Explanation

Stage VI Blount's disease indicates the presence of a medial physeal bar. Effective treatment requires resection of the bony bar, interposition of material (like fat or cranioplast) to prevent recurrence, and a corrective valgus osteotomy.

Question 3869

Topic: Pediatric Lower Extremity

Which of the following physical exam findings best differentiates a structural from a compensatory hindfoot varus in a patient with a rigid plantarflexed first ray (cavovarus foot)?

. Correction of the hindfoot varus on the Coleman block test
. Inability to stand on tiptoes
. Positive Silfverskiold test
. Correction of the varus with passive ankle dorsiflexion
. Absence of the windlass mechanism

Correct Answer & Explanation

. Correction of the hindfoot varus on the Coleman block test

Explanation

The Coleman block test drops the first ray off the block. If the hindfoot varus corrects to neutral or valgus, the deformity is flexible/compensatory (driven by the forefoot); if it remains in varus, the hindfoot deformity is fixed/structural.

Question 3870

Topic: 4. Pediatrics

During distraction osteogenesis, the optimal rate and rhythm of distraction established by Ilizarov to promote woven bone formation and minimize tissue ischemia is:

. 1.0 mm per day, divided into four 0.25 mm increments
. 2.0 mm per day, divided into two 1.0 mm increments
. 0.5 mm per day, divided into two 0.25 mm increments
. 1.5 mm per day in a single continuous adjustment
. 1.0 mm per day, divided into two 0.5 mm increments

Correct Answer & Explanation

. 1.0 mm per day, divided into four 0.25 mm increments

Explanation

Ilizarov's seminal research demonstrated that a rate of 1.0 mm/day is optimal. Dividing this into smaller, more frequent increments (rhythm), specifically 0.25 mm four times a day, provides continuous tension and minimizes ischemic damage to the regenerate.

Question 3871

Topic: 4. Pediatrics

What is the foundational principle underlying the Paley Multiplier method for predicting limb length discrepancy (LLD) in patients with congenital femoral deficiency?

. The rate of growth of the shortened limb decelerates progressively with skeletal age.
. The absolute length difference between the limbs increases by exactly 1 cm per year.
. The ratio of the length of the short limb to the normal limb remains constant throughout growth.
. The distal femoral physis in the affected limb closes an average of 2 years earlier than normal.
. The shortened limb grows at a fixed constant rate of 5 mm per year regardless of age.

Correct Answer & Explanation

. The ratio of the length of the short limb to the normal limb remains constant throughout growth.

Explanation

The Multiplier method is based on the principle of constant inhibition, meaning the ratio of the affected limb length to the normal limb length remains constant throughout skeletal growth. This constant ratio allows clinicians to accurately predict LLD at maturity using age- and sex-specific multipliers.

Question 3872

Topic: Pediatric Hip

A 2-week-old neonate presents with pseudoparalysis of the right lower extremity and crying upon diaper changes. Ultrasound confirms a significant hip effusion.

What is the most appropriate next step in management?

. Observation and repeat ultrasound in 1 week
. Pavlik harness application
. Intravenous antibiotics followed by MRI
. Immediate joint aspiration, arthrotomy, and irrigation
. Closed reduction and spica casting

Correct Answer & Explanation

. Immediate joint aspiration, arthrotomy, and irrigation

Explanation

Neonatal septic arthritis ('coxitis') is a surgical emergency that can rapidly destroy the cartilaginous femoral head. Immediate joint aspiration and urgent open arthrotomy with irrigation is required to prevent permanent joint destruction.

Question 3873

Topic: 4. Pediatrics

A 6-month-old infant with achondroplasia is noted to have brisk deep tendon reflexes and sleep apnea. What is the most common cause of mortality in this patient population during infancy?

. Cardiac conduction abnormalities
. Thoracic insufficiency syndrome
. Cervicomedullary compression at the foramen magnum
. Atlantoaxial instability
. Severe lumbar stenosis

Correct Answer & Explanation

. Cervicomedullary compression at the foramen magnum

Explanation

The most common cause of sudden death in infants with achondroplasia is cervicomedullary compression due to foramen magnum stenosis. Central sleep apnea and brisk reflexes are critical warning signs warranting urgent neurosurgical evaluation.

Question 3874

Topic: 4. Pediatrics

A 5-month-old infant presents with frontal bossing, rhizomelic shortening of the limbs, and midface hypoplasia. Which of the following describes the genetic etiology of this condition?

. Gain-of-function mutation in FGFR3
. Loss-of-function mutation in FGFR3
. Mutation in Type I Collagen (COL1A1/COL1A2)
. Mutation in the COMP gene
. Mutation in the RUNX2 gene

Correct Answer & Explanation

. Gain-of-function mutation in FGFR3

Explanation

Achondroplasia is the most common skeletal dysplasia, caused by a gain-of-function mutation in the FGFR3 gene. This mutation constitutively inhibits chondrocyte proliferation in the proliferative zone of the physis.

Question 3875

Topic: Pediatric Hip

A 3-week-old neonate presents with fever, irritability, and a pseudoparalysis of the right lower extremity. Ultrasound reveals a hip joint effusion.

What is the most appropriate next step in management?

. Pavlik harness application
. Urgent hip aspiration and surgical drainage
. Intravenous antibiotics and observation
. Closed reduction and spica casting
. MRI of the bilateral hips

Correct Answer & Explanation

. Urgent hip aspiration and surgical drainage

Explanation

Neonatal septic arthritis of the hip is a surgical emergency. Delay in decompression can lead to rapid destruction of the unossified femoral head (Tom Smith arthritis).

Question 3876

Topic: 4. Pediatrics

A 7-year-old girl is evaluated for recurrent long bone fractures after minimal trauma. She has blue sclerae and mild hearing loss. This condition is primarily caused by a defect in which of the following?

. Type II collagen
. Type X collagen
. Cartilage oligomeric matrix protein (COMP)
. Fibroblast growth factor receptor 3
. Type I collagen

Correct Answer & Explanation

. Type I collagen

Explanation

Osteogenesis imperfecta is characterized by brittle bones, blue sclerae, and hearing loss. It is caused by mutations in the COL1A1 or COL1A2 genes, which encode Type I collagen.

Question 3877

Topic: 4. Pediatrics

A newborn presents with severe bilateral clubfeet, 'hitchhiker' thumbs, and cystic swelling of the external ears (cauliflower ears). Which of the following genes is mutated in this condition?

. FGFR3
. COL2A1
. SLC26A2 (DTDST)
. COMP
. CBFA1

Correct Answer & Explanation

. SLC26A2 (DTDST)

Explanation

Diastrophic dysplasia is an autosomal recessive disorder caused by a mutation in the SLC26A2 sulfate transporter gene. Classic features include hitchhiker thumbs, cauliflower ears, and severe clubfeet.

Question 3878

Topic: 4. Pediatrics

An 8-year-old boy presents with a waddling gait and bilateral knee and hip pain. Radiographs reveal delayed ossification and irregularity of multiple epiphyses. Spine radiographs are completely normal. Mutation in which gene is most likely responsible?

. FGFR3
. COL1A1
. COL2A1
. COMP
. RUNX2

Correct Answer & Explanation

. COMP

Explanation

Multiple Epiphyseal Dysplasia (MED) involves irregular, delayed epiphyseal ossification but spares the spine, differentiating it from spondyloepiphyseal dysplasia. The most common mutation is in the COMP gene (Cartilage Oligomeric Matrix Protein).

Question 3879

Topic: 4. Pediatrics

A child born with normal length and facial features develops severe short stature and a waddling gait by age 3. Radiographs demonstrate small, irregular epiphyses and platyspondyly with anterior tongue-like projections of the vertebral bodies. Which of the following is the most likely diagnosis?

. Achondroplasia
. Hypochondroplasia
. Spondyloepiphyseal Dysplasia Congenita
. Mucopolysaccharidosis Type I
. Pseudoachondroplasia

Correct Answer & Explanation

. Pseudoachondroplasia

Explanation

Pseudoachondroplasia patients are normal at birth but develop significant dwarfism in early childhood. Unlike classic achondroplasia, they have normal facies but significant epiphyseal and spinal involvement (COMP mutation).

Question 3880

Topic: 4. Pediatrics

A 4-year-old child presents with a severe limb length discrepancy. Radiographs show complete destruction and absence of the capital femoral epiphysis and femoral neck on the right side.

This is the classic sequela of which untreated infantile condition?

. Developmental Dysplasia of the Hip
. Slipped Capital Femoral Epiphysis
. Tom Smith Arthritis
. Legg-Calve-Perthes Disease
. Proximal Focal Femoral Deficiency

Correct Answer & Explanation

. Tom Smith Arthritis

Explanation

Tom Smith arthritis refers to the complete destruction of the infant hip joint due to delayed or untreated neonatal septic arthritis. The cartilaginous anlage is rapidly destroyed by proteolytic enzymes.

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